We have prepared a panel of monoclonal antibodies specific for the neurotransmitter biosynthetic enzyme choline acetyltransferase. Anti-Drosophila choline acetyltransferase antibodies react with the enzyme active site while antibodies directed against the rat brain enzyme react with a small highly conserved non-active site region of the enzyme. Some of these antibodies cross react with both the Drosophila and rat brain enzymes and possibly with the human enzyme as well. We propose to study the function and significance of the highly conserved immunogenic region of choline acetyltransferase by using specific monoclonal antibodies as probes of the enzyme surface structure. We have also begun a molecular characterization of choline acetyltransferase protein from Drosophila and obtained information on the amino acid sequence of certain tryptic peptides. This limited structural information will be used to design synthetic oligonucleotide "probes" to identify and clone the gene for choline acetyltransferase. Once we have accomplished this goal we will be able to obtain complete structural information about the enzyme and begin to understand the control of its expression in developing, adult and senescent nervous system. Structural information and nucleic acid hybridization probes developed for the Drosophila gene will be used to clone the mammalian gene for choline acetyltransferase. The results of these proposed studies should be useful in understanding normal and abnormal chemical synaptic transmission at the molecular and cellular level in normal and pathological nervous system. Particularly relevant to this latter goal of our studies is the reported involvement of abnormal choline acetyltransferase levels in patients affected with senile dementia of the Alzheimer's type and the availability of structural gene mutants of Drosophila.